My Trials running app on App Engine uses SOLR for its search backend. We use Amazon EC2, S3 to host our inventory. We use a combination of Java, php for site. To minimize server expenditures, I thought of leveraging Google App Engine. So, started experimenting with php using Quercus framework. Though I got most of the pages working fine, some external url’s are failing with a invalid string exception. I thought of modifying com.caucho.quercus.servlet.GoogleQuercusServlet in resin.jar , but could not get hold of source for resin.jar. As always, because of time constraints, could not get to the bottom of the problem.